1. Field of the Invention
The present invention relates to an air inlet lip for a turbojet pod, which is to be attached to a downstream air inlet structure and which comprises at least one electric heating element for de-icing, together with a corresponding downstream structure; the invention also relates to a turbojet pod comprising an air inlet according to the invention.
2. Description of Related Art
An aircraft is propelled by one or more propulsion units, each comprising a turbojet housed in a tubular pod. Each propulsion unit is attached to the aircraft by a pylon which is generally located under a wing or on the fuselage.
The structure of a pod generally comprises an air inlet upstream of the engine, a mid-section designed to enclose a turbojet fan, and a downstream section housing thrust reversal means and designed to enclose the combustion chamber of the turbojet, and generally terminates in a jet nozzle whose outlet is located downstream of the turbojet.
The air inlet comprises, on the one hand, an inlet lip adapted in such a way that the air required for the supply of the fan and the internal compressors of the turbojet is captured and guided towards the turbojet in an optimal way, and, on the other hand, a downstream structure onto which the lip is fitted and which is designed to channel the air appropriately towards the blades of the fan. The assembly is attached upstream of a fan casing belonging to the upstream section of the pod.
In flight, depending on the temperature and humidity, ice may form on the pod at the position of the air inlet lip. The presence of ice or frost modifies the aerodynamic properties of the air inlet and perturbs the guidance of air towards the fan. Furthermore, fragments of ice may possibly break away from the air inlet lip and collide with components of the turbojet such as the fan blades.
Moreover, the air inlet lip is a component which is subject to numerous impacts with external elements such as grit, birds, hail, etc., which can damage the aerodynamic integrity of the outer surface and lead to premature wear.
Since the performance of the turbojet is dependent on the quantity and quality of the air capture provided by the air inlet, a defective lip must be replaced as rapidly as possible. Such a replacement is a time-consuming and expensive maintenance operation, since it is possible for only one part of the lip to be damaged.
In a first method for de-icing an air inlet lip, hot air is drawn from the turbojet compressor and directed to the inlet lip, where it heats the walls by flowing through an internal channel in the air inlet lip. However, a device of this kind requires a system for conveying the hot air between the turbojet and the air intake, as well as a system for discharging the hot air at the air inlet lip. This increases the weight of the propulsion unit, which is undesirable. A further consequence of this system is that, in order to avoid having a multiplicity of hot air intakes and outlets, the air inlet lip is made in one piece having a continuous peripheral internal passage for the flow of the hot air, and therefore the whole component has to be changed if its outer profile is damaged.
A second method, described in EP 1 495 963, is that of applying a heating resistor to an outer wall of the air inlet lip, this resistor being supplied from a power source in the pod. This technology enables a modular air inlet lip to be formed from a plurality of basic structures. Although less complicated, the changing of one or more structures is still time-consuming because of the need to reconnect the power supply means of the structure.
According to EP 1 175 160 and EP 1 715 159, the replacement of the lip can be facilitated by producing an air inlet lip designed to be attached to a downstream air inlet structure and comprising at least one electric heating element for de-icing, characterized in that said electric heating element is provided with at least one electrical connector which can be connected to at least one corresponding power supply connector of the downstream structure. Thus the provision of electrical connectors greatly facilitates the assembly of the air inlet lip, and particularly the restoration of the electrical connections, since it is simply necessary to plug each electrical connector of the lip into the corresponding power supply connector, as in any electrical plug and socket system, in order to restore the continuity of the electrical circuit.